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Table 3 Summary characteristics of Antibodies to Nucleocapsid protein (anti-N) during first re-infection events occurring during the observation window (n = 118 of n = 129 re-infection events overall), by identification method, vs. a randomly selected interview following incident infection and without evidence of re-infection (n = 200)

From: Enhancing detection of SARS-CoV-2 re-infections using longitudinal sero-monitoring: demonstration of a methodology in a cohort of people experiencing homelessness in Toronto, Canada

 

Random interview without evidence of re-infection (N = 200)

First re-infection event

Identified through longitudinal serology only (N = 90)

Identified through testing (N = 28)

Anti-N RRain previous interview

Mean (SD) RR

1.06 (1.08)

0.70 (0.74)

0.64 (0.85)

Median (IQR) RR

0.64 (0.39–1.57)

0.40 (0.24–0.84)

0.45 (0.13–0.69)

Anti-N RRaduring interview

Mean (SD) RR

0.9 (0.92)

2.32* (1.39)

1.81 (1.61)

Median (IQR) RR

0.56 (0.3–1.17)

2.31* (0.94–3.49*)

1.23 (0.40–3.31*)

Differencebin anti-N RRabetween interviews

Mean (SD) RR

-0.19 (0.88)

1.62 (1.21)

1.16 (1.60)

Median (IQR) RR

-0.14 (-0.44–0.03)

1.29 (0.48–2.79*)

0.58 (-0.08–2.67*)

Ratiocin anti-N RRabetween interviews

Mean (SD) RR

1.45 (3.74)

6.21 (6.89)

5.93 (8.19)

Median (IQR) RR

0.79 (0.57–1.12)

3.64 (1.99–7.18)

3.17 (0.86–6.62)

Days between infections

Mean (SD)

N/A

322.82 (147.50)

360.97 (142.10)

Median (IQR)

N/A

315.94 (209.40–414.00)

338.57 (280.30–448.00)

  1. Anti-N = Antibodies to Nucleocapsid protein; RR = Relative Ratio; IQR = Interquartile Range
  2. aAnti-N relative ratios are derived from the blood sample (plasma or dried blood spot) ELISA, primary dilution (1:160 (0.0625µL/well) only
  3. bDifference in anti-N RR represents [anti-N RR at selected interview– anti-N RR at immediately preceding interview]
  4. cRatio in anti-N RR represents [anti-N RR at selected interview / anti-N RR at immediately preceding interview]
  5. *Value is outline of the linear range of the assay: results are thus likely an underestimate of true levels